I'm not sure if your (good) questions are legitimate and about the site or rhetorical and about the quality of reportage. If it's the former, then:
WHY did they create this site?
They didn't. It was forked from Wikitravel several years ago.
What's the motivation for creating a second one that has the same content?
Free culture. This site is run on a non-profit basis. At the risk of sounding pedantic, it's worth it to have free alternatives. This is like saying, "We already have a newspaper, so why have alternative weeklies?"
And why do all the articles about Wikivoyage neglect to mention Wikitravel?
That's maybe your best question and providing context to these stories will help to clarify *why* this is news at all. The Wikimedia Foundation probably doesn't mention them in their press because of litigious threats and the fact that Wikivoyage has (and has had) its own identity, but news outlets should do their research and post background information making your questions redundant rather than simply parroting press releases.